In U.S. Pat. No. 4,708,681, issued Nov. 24, 1987, for "Method of Making a Long Lived High Current Density Cathode From Tungsten and Iridium Powders", to L. E. Branovich, G. L. Freeman, and B. Smith, and assigned to a common assignee, there is disclosed and claimed a method of making a long life high current density cathode suitable for operation in millimeter wave and microwave devices in which a mixture of tungsten and iridium powders is processed with an activator into a porous billet, and the porous billet then impregnated with a chemical mixture of barium oxide, strontium oxide and aluminum oxide by firing the billet in a dry hydrogen furnace at a temperature at which the impregnant melts.
In U.S. Pat. No. 4,735,591, issued Apr. 5, 1988 for "Method of Making a Long Life High Current Density Cathode From Tungsten and Iridium Powders Using a Barium Iridiate as the Impregnant", to L. E. Branovich, G. L. Freeman and B. Smith, and assigned to a common assignee, there is disclosed and claimed a method of making a long life high current density cathode suitable for operation in millimeter and microwave devices in which a mixture of tungsten and iridium powders is processed with an activator into a porous billet, and the porous billet then impregnated with barium iridiate by firing the billet in a dry hydrogen furnace at a temperature at which the impregnant melts.
This application is also copending with U.S. patent application Ser. No. 213,035, filed June 27, 1988, for "Method of Making a Long Life High Current Density Cathode From Tungsten and Osmium Powders Using a Barium Osmiate as the Impregnant", by L. E. Branovich, G. L. Freeman and B. Smith, and assigned to a common assignee. In that application, there is disclosed and claimed a method of making a long life high current density cathode suitable for operation in millimeter wave and microwave devices in which a mixture of tungsten and osmium powders is processed with an activator into a porous billet, and the porous billet then impregnated with a barium osmiate by firing the billet in a dry hydrogen furnace at a temperature at which the impregnant melts.
Though the cathodes prepared by the methods of U.S. Pat. Nos. 4,708,681 and 4,735,591 and Ser. No. 213,035, have desirable emission characteristics, it would be even more desirable to provide a method of making a cathode having an even longer life and a higher current density.